Autodepositable aqueous compositions including dispersed non-film-forming polymers

ABSTRACT

An autodepositing liquid composition comprises dispersed non-film-forming polymer particles in addition to the dispersed film forming polymer characteristic of all autodepositing liquid compositions. Preferably, the non-film-forming polymer particles are gas-tight microballoons filled with a gas such as air and have an average particle size less than 1 μm. Such particles act in the autodepositing liquid compositions and in the dried coatings formed from them as opaque white pigments, unless the coatings are heated above about 130° C., if so heated, the coatings, unless they contain other heat stable pigment, become irreversibly transparent.

This application is a 371 of PCT/US99/22069 filed on Sep. 23, 1999 whichclaims benefit of Ser. No. 60/101,550 filed on Sep. 23, 1998.

FIELD AND BACKGROUND OF THE INVENTION

This invention relates to the use of autodepositable aqueous liquidcompositions that are both dispersions and solutions in water. By merecontact with these autodepositable liquid compositions, active metalsurfaces can be coated with an adherent polymer film that increases inthickness the longer the time of contact, even though the aqueous liquidcomposition is stable for a long time against spontaneous precipitationor flocculation of any solid phase, in the absence of contact withactive metal. (For the purposes of this specification, the term “activemetal” is to be understood in its broadest sense as including all metalsand alloys more active than hydrogen in the electromotive series, or, inother words, a metal which is thermodynamically capable of dissolving toproduce dissolved cations derived from the metal, with accompanyingevolution of hydrogen gas, when contacted with an aqueous solution of anon-oxidizing acid in which the activity of hydrogen ions is 1.00equivalent per liter.) Such liquid compositions are denoted in thisspecification, and commonly in the art, as “autodeposition” or“autodepositing” compositions, dispersions, emulsions, suspensions,baths, solutions, or a like term. Autodeposition is often contrastedwith electrodeposition, which can produce very similar adherent filmsbut requires that the surface to be coated be connected to a source ofdirect current electricity for coating to occur.

It is generally believed in the art that autodeposition works becausethe cations dissolving from the metal surface to be coated are, ofcourse, initially confined to the volume of contacting liquid in theimmediate vicinity of the metal surface from which they are dissolving,and these recently dissolved cations interact with the liquidautodepositing composition in at least one of the following ways: (i)The dissolved cations precipitate previously dissolved polymers bydisplacing previously associated cations or cation-forming moieties, inassociation with which the polymers are soluble, by the newly dissolvedcations in association with which the polymers are much less soluble;and/or (ii) the dissolved cations destabilize numerous individualdispersed phase units in a dispersion of a polymer with inherently lowwater solubility, which nevertheless can remain in stable suspension fora long time in the absence of dissolved polyvalent cations, because theouter surfaces of the dispersed phase units carry a net negativeelectrical charge, derived from anionic components of the dispersedpolymer itself and/or from an anionic dispersing agent used to preparethe autodepositing composition in question. The net negative charge onthe units of the dispersed phase in an autodepositing liquid compositionis believed to be electrically counterbalanced by a diffuse excess ofcations, usually monovalent cations, in the surrounding continuous phaseof the dispersion. This excess of cations together with the negativecharges on the dispersed phase units constitutes an example of the wellknown “electrical double layer” or “Helmholz double layer” that ischaracteristic of most interfaces between liquid phases containingcharged solute particles and solids in contact with such liquid phases.As long as this double layer remains intact, the net negative charge onthe exterior of each unit of the dispersed phase causes it to repelother units of the dispersed phase that also carry a net negativecharge, and thereby prevents spontaneous coalescence of the dispersedphase units.

When the double layer is sufficiently disturbed (or in the case of asoluble polymer, when the solubility is reduced) by introduction of newcations, the polymeric parts of numerous dispersed phase units and/orsolute polymer molecules aggregate. Aggregated polymer molecules, alongwith some of the liquid in which they were dissolved or dispersed, forminitially a wet coating layer with at least sufficient cohesion toresist completely draining away under the influence of the Earth'sgravity. Upon further drying, this wet coating layer forms a continuousdry solid film, if the chemical nature of the polymer favors such atransition and the temperature during drying is sufficiently far abovethe glass transition temperature of the polymer concerned. Polymers thathave this property of forming a continuous solid film or body frominitially finely dispersed or dissolved particles of the polymer in aliquid dispersion medium or solvent are defined as “film-forming”polymers, and at least one such polymer is a necessary constituent ofevery conventional autodeposition bath. The continuous solid film formedby the film-forming polymer content of an autodeposition bath mayconstitute the entire solidified and cured autodeposited coating, andany instance normally constitutes the only continuous solid phase of thesolidified and cured autodeposited coating. It is quite common for acured autodeposited coating also to include at least one discontinuousphase, most often a pigment such as carbon black.

In other kinds of polymers, both coatings and solid objects, it iscommon to include a discontinuous solid phase, usually called “filler”or “reinforcement”, that is dispersed in the continuous polymer phaseand acts to alter the properties of the composite formed by thecontinuous and discontinuous solid phases from those that prevail in thecontinuous phase only. In many instances, it is possible both to reducethe cost per unit volume and to increase the mechanical strength byincluding in a polymer a mineral filler such as clay, calcium carbonate,or the like. Although the inclusion of such materials in anautodeposited coating has been taught in prior patents, it is notbelieved that any use of dispersed solid phases in autodeposition bathshas attained profitably practical success for any purpose exceptpigmentation. The use of two or more types of film-forming resins in anautodeposition bath has also been taught, but again is not believed tohave achieved profitably practical success.

One major object of this invention is to provide autodepositing liquidcompositions from which it is possible to deposit on contacted metalsurfaces coatings that contain dispersed solid phases, which provide forautodeposited coatings at least some of the advantages practicallyachieved in other uses of polymers by the inclusion of fillers and/or bythe use of composite structures containing more than one type ofpolymer. Other alternative and/or concurrent objects will be apparentfrom the further description below.

Except in the claims and the operating examples, or where otherwiseexpressly indicated, all numerical quantities in this descriptionindicating amounts of material or conditions of reaction and/or use areto be understood as modified by the word “about” in describing thebroadest scope of the invention. Practice within the numerical limitsstated is generally preferred, however. Also, throughout thedescription, unless expressly stated to the contrary: percent, “partsof”, and ratio values are by weight or mass; the term “polymer” includes“oligomer”, “copolymer”, “terpolymer” and the like; the description of agroup or class of materials as suitable or preferred for a given purposein connection with the invention implies that mixtures of any two ormore of the members of the group or class are equally suitable orpreferred; description of constituents in chemical terms refers to theconstituents at the time of addition to any combination specified in thedescription or of generation in situ within the composition by chemicalreaction(s) noted in the specification between one or more newly addedconstituents and one or more constituents already present in thecomposition when the other constituents are added, and does not precludeunspecified chemical interactions among the constituents of a mixtureonce mixed; specification of constituents in ionic form additionallyimplies the presence of sufficient counterions to produce electricalneutrality for the composition as a whole and for any substance added tothe composition; any counterions thus implicitly specified preferablyare selected from among other constituents explicitly specified in ionicform, to the extent possible; otherwise such counterions may be freelyselected, except for avoiding counterions that act adversely to anobject of the invention; the word “mole” means “gram mole”, and the worditself and all of its grammatical variations may be used for anychemical species defined by all of the types and numbers of atomspresent in it, irrespective of whether the species is ionic, neutral,unstable, hypothetical, or in fact a stable neutral substance with welldefined molecules; the terms “solution”, “soluble”, “homogeneous”, andthe like are to be understood as including not only true equilibriumsolutions or homogeneity but also dispersions that show no visuallydetectable tendency toward phase separation over a period of observationof at least 100, or preferably at least 1000, hours during which thematerial is mechanically undisturbed and the temperature of the materialis maintained within the range of 18-25° C.; and the first definition ofan acronym or other abbreviation applies to all subsequent uses of thesame acronym or other abbreviation.

BRIEF SUMMARY OF THE INVENTION

It has been found that at least one of the major objects of theinvention can be achieved by including in an autodeposition bath asuitable quantity of non-film-forming dispersed organic material thatcodeposits with the film-forming-resin(s) also present in theautodeposition bath into the wet autodeposited film.

DETAILED DESCRIPTION OF THE INVENTION

An autodepositing liquid composition according to the present inventioncomprises, preferably consists essentially of, or more preferablyconsists of, water and the following components:

(A) at least 1.0%, based on the whole composition, of a component ofdissolved, dispersed, or both dissolved and dispersed film formingpolymer molecules;

(B) an emulsifying agent component in sufficient quantity to emulsifyany water insoluble part of any other component so that, in theautodepositing liquid composition, no separation or segregation of bulkphases that is perceptible with normal unaided human vision occursduring storage at 25° C. for at least 24 hours after preparation of theautodepositing liquid composition, in the absence of contact of theautodepositing liquid composition with any metal that reacts with theautodepositing liquid composition to produce therein dissolved metalcations with an electrical charge of at least two;

(C) a dissolved accelerator component selected from the group consistingof acids, oxidizing agents, and complexing agents that are not part ofimmediately previously recited components (A) or (B), this acceleratorcomponent being sufficient in oxidizing tendency and amount to impart tothe total autodepositing liquid composition an oxidation-reductionpotential that is at least 100 millivolts (hereinafter usuallyabbreviated as “mV”) more oxidizing than a standard hydrogen electrode;and

(D) a component of dispersed non-film-forming organic particles that arenot part of any of immediately previously recited components (A) through(C); and, optionally, one or more of the following components:

(E) a component of pigment, filler, or other dispersed solid phasematerials other than materials that constitute any part of any ofimmediately previously recited components (A) through (D);

(F) a component of dyes or other dissolved coloring materials other thanmaterials that constitute any part of immediately previously recitedcomponents (A) through (E);

(G) a component of coalescing agent, other than materials thatconstitute any part of immediately previously recited components (A)through (F);

(H) a component of solvent, other than materials that form any part ofimmediately previously recited components (A) through (G), in which atleast one constituent of either or both of components (A) and (D) thatis insoluble in water was dissolved during some operation in thepreparation of the autodepositing liquid composition; and

(J) a plasticizer component, other than materials that constitute partof immediately previously recited components (A) through (H).

In this description: The phrase “dispersed or dissolved and dispersedfilm forming polymer molecules” means that the molecules so described,when separated from any other materials with which they may beco-dispersed or co-dissolved and co-dispersed and in the form of a layerat least 5 millimeters thick of a homogeneous liquid mixture in whichthe polymers constitute at least 5% of the mass of the mixture, willspontaneously form a continuous body that is solid at 30° C. upon dryingor other removal of the water, at a temperature of at least 30° C., fromsaid layer; the term “component of solvent” means a single phase,consisting of a single chemical substance or a mixture of chemicalsubstances, that (i) is liquid at 25° C. and (ii) is not constitutedexclusively of water and inorganic solutes only; and the term“coalescing agent” means a material that (i) is liquid at 100° C., (ii)has a boiling point at normal atmospheric pressure that is at least 110°C. or preferably, with increasing preference in the order given, atleast 120, 130, 140, 150, 160, or 165° C. and independently is not morethan 300° C., or preferably, with increasing preference in the ordergiven, not more than 290, 280, 270, 265, 260, 255, 250, 245° C., and(iii) promotes the formation of dry coatings without coatingirregularities (such as craters, popped blisters, thick spots, barespots, or the like) that are readily detectable with normal unaidedhuman vision, as determined by comparison of the density of coatingirregularities obtained, under identical processing conditions, by(iii.i) autodeposition from an autodepositing liquid compositioncontaining the material being tested for its coalescing properties,followed by cure of the film thus deposited and (iii.ii) an otherwiseidentical process in which the material being tested for its coalescingproperties is replaced, in the autodepositing liquid composition used inthe process, by an equal mass of water.

In addition to a complete autodepositing liquid composition as describedabove, another embodiment of the invention is a liquid replenishercomposition useful to replace film forming polymer and other materialsconsumed by use of an autodepositing liquid composition according to theinvention and/or to make a working composition according to theinvention by dilution with water and, optionally, addition of othermaterials. Such a liquid replenisher composition according to theinvention comprises, preferably consists essentially of, or morepreferably consists of, water and:

(A′) at least 10%, based on the whole composition, of dissolved,dispersed, or both dissolved and dispersed film forming polymermolecules;

(B′) an emulsifying agent component in sufficient quantity to emulsifyany water insoluble part of any other component so that, in the liquidreplenisher composition, no separation or segregation of bulk phasesthat is perceptible with normal unaided human vision occurs duringstorage at 25° C. for at least 24 hours after preparation of the liquidreplenisher composition, in the absence of contact of the liquidreplenisher composition with any metal that reacts with the liquidreplenisher composition to produce therein dissolved metal cations witha charge of at least two; and

(D′) a component of dispersed non-film-forming organic particles thatare not part of either of immediately previously recited components (A′)or (B′); and, optionally, one or more of the following components:

(C′) a dissolved accelerator component selected from the groupconsisting of acids, oxidizing agents, and complexing agents that arenot part of any of immediately previously recited components (A′), (B′),or (D′),

(E′) a component of pigment, filler, or other dispersed solid phasematerials other than the materials that constitute any part of any ofimmediately previously recited components (A′) through (D′);

(F′) a component of dyes or other dissolved coloring materials otherthan materials that constitute any part of immediately previouslyrecited components (A′) through (E′);

(G′) a component of coalescing agent, other than materials thatconstitute any part of immediately previously recited components (A′)through (F′);

(H′) a component of solvent, other than materials that form any part ofimmediately previously recited components (A′) through (G′), in whichconstituents of either or both of components (A′) and (D′) that areinsoluble in water were dissolved during some operation in thepreparation of the liquid replenisher composition; and

(J′) a plasticizer component, other than materials that constitute partof immediately previously recited components (A′) through (H′).

Ordinarily each component of a preferred replenisher compositionidentified by a primed letter immediately above will preferably have thesame chemical composition for each component as for the component withthe same unprimed letter in the working composition, as describedfurther above, that is to be replenished with or made up from thereplenisher composition. Therefore, the description below of preferredconstituents for each component and subcomponent thereof in chemicalterms will be given explicitly only for unprimed components andsubcomponents, but applies equally to primed components with the sameletter unless otherwise stated. The ratios among the various components,however, may be different between replenisher and working compositions,in order to compensate for more rapid consumption of some constituentsof a working composition than for other constituents of the samecomposition when the working composition is used. Ratios between oramong subcomponents of a single major component may also be different inthe replenisher than in the working composition that is replenished withit, if the rates of consumption of the subcomponents from a workingautodepositing liquid composition are not in proportion to theconcentrations of these ingredients in the working autodepositing liquidcomposition. In all cases, the concentrations of all components exceptwater that are present in a replenisher composition normally preferablyare larger than the concentration for the corresponding component in anautodepositing liquid working composition according to the invention bya factor that is at least, with increasing preference in the ordergiven, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 and independentlypreferably is not more than, with increasing preference in the ordergiven, 20, 15, 10, 8, or 6. If the concentration of components otherthan water in a replenisher composition is too low, the cost of shippingit will be higher than is economically justified, while if theconcentration of these components is too high, storage stability will bereduced.

A replenisher composition as described immediately above that is to bestored for several weeks or more before use preferably does not containoptional component (C′) or any subcomponents thereof as described below,because all of these subcomponents are detrimental to storage stabilityof the replenisher composition. The accelerator components are thereforepreferably provided to a working autodepositing liquid compositionaccording to this invention from at least one separate replenishercomposition to maintain substantially constant values of oxidizing powerand fluoride

Components (A), (B), and (C) as described above are conventional forautodeposition baths, and suitable and preferred chemical compositionsfor them are taught in one of more of the following U.S. Patents andPatent Applications, the entire disclosures of which, to the extent notcontrary to any explicit statement herein, are hereby incorporatedherein by reference: application Ser. No. 09/029,708, now abandoned, andapplication Ser. No. 08/740,522; International Application NumberPCT/US96/12540; and U.S. Pat. Nos. 6,143,365, 6,033,492, 5,945,170,5,786,030, 5,760,624, 5,688,560, 5,667,845, 5,646,211, 5,578,199,5,545,319, 5,538,644, 5,372,853, 5,510,410, 5,427,863, 5,409,737,5,393,416, 5,385,798, 5,372,853, 5,342,694, 5,300,323, 5,248,525,5,164,234, 5,114,751, 5,080,937, 5,061,523, 5,011,715, 4,994,521,4,800,106, 4,758,621, 4,661,385, 4,637,839, 4,632,851, 4,564,536,4,562,098, 4,554,305, 4,414,350, 4,411,950, 4,373,050, 4,366,195,4,357,372, 4,347,172, 4,318,944, 4,243,704, 4,242,379, 4,229,492,4,206,169, 4,199,624, 4,191,676, 4,186,226, 4,186,219, 4,178,400,4,177,180, 4,160,756, 4,108,817, 4,104,424, 4,030,945, 4,012,351,3,960,610, 3,955,532, 3,936,546, 3,914,519, 3,839,097, 3,795,546,3,776,848, 3,791,431, 3,592,699, and 3,585,084.

In a first especially preferred embodiment of this invention, a polymermolecule of component (A) preferably includes a subcomponent¹ (A1)selected from residues of

¹The term “subcomponent” when used herein does not necessarily implythat the material so designated can not constitute the entire componentof which it is described as a subcomponent, except when furtherqualified, for example by specifying a portion less than 100% of thetotal component that is constituted by the subcomponent. In thisparticular instance, the term subcomponent refers to one or moreportions of a single polymer molecule having a particular structureidentifiable as a “residue” of a particular kind of monomer thatincludes a polymerizable carbon-carbon double bond. A chemical compound(monomer) conforming to the general chemical formula:

where each of M¹, M², M³, and M⁴ independently represents any monovalentmoiety, provided that the moieties do not preclude additionpolymerization of the double bond shown in the general formula, when itis polymerized forms a moiety conforming to the general chemicalformula:

where each of M¹ through M⁴ has the same meaning as in the generalformula for the compound given next above and the open bonds shown onthe carbon atoms are attached to other moieties of the polymer molecule.This moiety is defined as the “residue” in the polymer molecule of thecompound or monomer conforming to the general chemical formula firstshown in this note.

polymerization of acrylic and methacrylic acids and the salts of both ofthese acids, in order to promote cross-linking reactions during thedrying and curing of the autodeposited coatings eventually formed.Methacrylic acid is most preferred for this subcomponent. The averagepercentage of residues of subcomponent (A1) in component (A) overallpreferably is at least, with increasing preference in the order given,0.50, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 4.9 and independentlypreferably is not more than, with increasing preference in the ordergiven, 15, 10, 9.0, 8.0, 7.0, 6.5, 6.0, 5.5, or 5.1. If the percentageof subcomponent (A1) is too low, the autodeposited coating formed islikely to have less heat resistance than is desired, while if thispercentage is too high, the autodeposited coating formed is likely to bemore susceptible to damage from mechanical shocks than is desired.

A polymer molecule of component (A) for this first especially preferredembodiment preferably further includes a subcomponent (A2) selected fromresidues of polymerization of esters of acrylic and methacrylic acidswith alcohols that contain at least, with increasing preference in theorder given, 4, 5, 6, 7, or 8 carbon atoms per molecule andindependently preferably contain not more than, with increasingpreference in the order given, 20, 18, 16, 14, 12, or 10 carbon atomsper molecule. Further and independently, the alcohols corresponding tothe esters of subcomponent (A2) preferably are not straight chainalcohols, but instead preferably contain at least one branch off thelongest carbon-carbon chain in a molecule of the alcohol, this branchindependently being most preferably in the 2 position and preferably atleast two carbon atoms long. Residues of 2-ethylhexyl acrylate are mostparticularly preferred for this subcomponent. Independently of its exactchemical nature, the percentage of the total component (A) that isconstituted of subcomponent (A2) portions of the molecules thatconstitute component (A) preferably is at least, with increasingpreference in the order given, 5, 10, 15, 20, 23, 26, 29, or 32 andindependently preferably is not more than, with increasing preference inthe order given, 60, 50, 45, 42, 39, 36, or 34. If the percentage ofsubcomponent (A2) is too low, the autodeposited coating formed is likelyto be more susceptible to damage from mechanical shock than isdesirable, while if the percentage of subcomponent (A2) is too high, theheat resistance of the autodeposited coating formed is likely to belower than is desirable.

Molecules of component (A) for this first especially preferredembodiment of the invention further preferably, primarily for reasons ofeconomy, include a subcomponent (A3) selected from residues ofaddition-polymerizable hydrocarbon molecules, which more preferably, inorder to promote heat resistance of the autodeposited coating eventuallyformed, are molecules of hydrocarbons including an aromatic nucleus. Thesingle most preferred hydrocarbon comonomer is styrene. The percentageof subcomponent (A3) in component (A) as a whole preferably is at least,with increasing preference in the order given, 10, 15, 20, 23, 26, 29,32, or 35 and independently preferably is not more than, with increasingpreference in the order given, 60, 50, 47, 44, 41, or 38. If thepercentage of subcomponent (A3) is too large, both heat resistance andsusceptibility to damage from mechanical shocks are likely to be lowerthan desirable for the autodeposited coatings formed from thecomposition, while if the percentage of subcomponent (A3) is too low,the coatings produced will usually be more costly than is economicallyjustified by any performance improvement observed.

Molecules of component (A) for this first especially preferredembodiment of the invention further preferably include a subcomponent(A4) of residues of acrylic monomers that are not part of eithersubcomponent (A1) or (A2) as described immediately above. The singlemost preferred residues are those of acrylonitrile. The percentage ofsubcomponent (A4) in component (A) as a whole preferably is at least,with increasing preference in the order given, 5, 10, 13, 15, 17, 19,21, or 23 and independently preferably is not more than, with increasingpreference in the order given, 50, 45, 40, 35, 32, 30, 28, or 26.

In a second especially preferred alternative embodiment, component (A)is selected from molecules including residues of vinylidene chloride toconstitute from 50 to 99% of the mass of the molecules and residues ofsulfoethylmethacrylate to constitute from 0.1 to 5% of the mass of themolecules, optionally also including residues of one or more othercomonomers selected from the group consisting of vinyl chloride,acrylonitrile, acrylamides, and methacrylamides.

Component (B) as described above may be incorporated into component (A)by copolymerizing with the other monomers described for component (A) anionic significantly water-soluble material which is selected from thegroup of sulfonic acids and their salts having the following generalformula:

R—Q¹—Q²—(SO₃)⁻M⁺

wherein the moiety “R” is selected from the group consisting of vinyland substituted vinyl, for example, alkyl-substituted vinyl; the symbol“Q¹” represents a difunctional linking group which will activate thedouble bond in the vinyl group; “Q²” represents a divalent hydrocarbonmoiety having its valence bonds on different carbon atoms; and thesymbol “M⁺” represents a cation. Sodium sulfoethyl methacrylate of theformula:

is a highly preferred copolymerizable material for use as component (B)to form “self-emulsifying” polymers or “self-stabilizing” latexes. Moredetails about using this type of emulsifying component are given in U.S.Pat. No. 4,800,106 of Jan. 24, 1989, column 7 line 45 through column 8line 49. Contrary to the state of the autodeposition art when usingcoating resins that contain predominantly vinylidene chloride residues,however, if acrylic coating resins are used in this invention,conventional external emulsifying agents are usually as satisfactory asthe internal emulsifying agents that are copolymerized as part of thepolymer molecules themselves. More particularly, the emulsifying agentsand amounts thereof used by commercial suppliers of acrylic latexes aregenerally satisfactory and preferred for use in this invention, thepreference being primarily due to cost savings from not having toprepare a special polymer for use in autodeposition only. Thesecommercially used emulsifying agents are usually proprietary, but theyare all believed to be anionic surfactants and most are believed toinclude arylsulfonic acid groups.

Accelerator component (C) as described above may be selected from anymaterial or combination of materials known for the purpose in priorautodeposition art or otherwise found to give satisfactory results. Themost preferred component (C) contains the following three subcomponents:

(C1) a concentration of fluoride ions that in a working autodepositionbath is at least, with increasing preference in the order given, 0.4,0.8, 1.0, 1.2, 1.40, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, or 1.79 gramsof fluoride ions per liter of total autodeposition bath, a concentrationunit that may be used hereinafter for any other constituent as well asfor fluoride ions and is hereinafter usually abbreviated as “g/l” andindependently preferably is not more than, with increasing preference inthe order given, 5, 4.0, 3.6, 3.3, 3.0, 2.8, 2.60, 2.50, 2.40, 2.30,2.25, 2.20, 2.15, 2.10, 2.05, 2.00, 1.95, 1.90, or 1.85 g/l of fluorideions (the entire fluorine atom content of any source of fluorine inanions dissolved in an autodeposition bath according to the invention isto be considered as fluoride ions for the purpose of testing conformanceto these preferred concentrations of fluoride ions, irrespective of theactual extent of ionization, aggregation, formation of complex ions, orthe like that may occur);

(C2) an amount of oxidizing agent, preferably selected from the groupconsisting of hydrogen peroxide and ferric ions, sufficient to provideto the working autodepositing liquid composition an oxidation potential,measured by the potential of a platinum or other inert metal electrodein contact with the autodepositing liquid composition, that is, withincreasing preference in the order given, at least 150, 175, 200, 225,250, 275, 300, 325, 340, or 350 mV more oxidizing than a standardhydrogen electrode and independently preferably is, with increasingpreference in the order given, not more than 550, 525, 500, 475, 450,425, 410, or 400 mV more oxidizing than a standard hydrogen electrode;and

(C3) a source of hydrogen cations in an amount sufficient to impart tothe autodeposition bath a pH that is at least, with increasingpreference in the order given, 1.0, 1.4, 1.6, 1.8, or 2.0 andindependently preferably is not more than, with increasing preference inthe order given, 3.8, 3.6, 3.4, 3.2, 3.0, 2.8, or 2.6.

It should be understood that subcomponents (C1) through (C3) need notall be derived from different materials. Hydrofluoric acid, inparticular, is preferred as a source for both (C1) and (C3), and ferricfluoride, which can be made by dissolving iron in hydrofluoric acid, cansupply both (C1) and (C2).

Most preferably, ferric cations, hydrofluoric acid, and hydrogenperoxide are all used to constitute component (C). In a workingcomposition according to the invention, independently for eachconstituent: the concentration of ferric cations preferably is at least,with increasing preference in the order given, 0.5, 0.8, 1.0, 1.20,1.30, 1.40, or 1.45 g/l and independently preferably is not more than,with increasing preference in the order given, 2.95, 2.90, 2.85, 2.80,2.75, 2.70, 2.65, 2.60, 2.55, or 2.50 g/l; the concentration of fluorinein anions preferably is at least, with increasing preference in theorder given, 0.5, 0.8, 1.0, 1.2, 1.4, 1.50, 1.55, 1.60, 1.65, 1.70,1.75, or 1.79 g/l and independently preferably is not more than, withincreasing preference in the order given, 10, 7.0, 5.0, 4.0, 3.0, 2.75,2.50, 2.40, 2.30, 2.20, 2.15, 2.10, 2.05, 2.00, 1.95, 1.90, 1.85, or1.81 g/l; and the amount of hydrogen peroxide added² to a freshlyprepared working composition preferably is at least, with increasingpreference in the order given, 0.050, 0.10, 0.20, 0.30, 0.40, 0.50,0.54, or 0.57 g/l and independently preferably is not more than, withincreasing preference in the order given, 2.1, 1.8, 1.5, 1.2, 1.00,0.90, 0.80, 0.70, 0.65, or 0.61 g/l.

²Because of numerous chemical reactions, including spontaneousdecomposition, in which hydrogen peroxide can participate, itsconcentration as analytically determined will often be considerably lessthan corresponds to the amount added.

Component (D) as described above preferably comprises, more preferablyconsists essentially of, or still more preferably consists of, particleswith an average particle size (i.e., largest linear dimension) that isat least, with increasing preference in the order given, 0.05, 0.10,0.20, 0.25, 0.30, 0.35, or 0.40 micrometres (hereinafter usuallyabbreviated as “μm”) and independently preferably is not more than, withincreasing preference in the order given, 4.0, 3.0, 2.0, 1.0, 0.80,0.70, 0.65, 0.60, or 0.55 μm. Independently of the actual size, a narrowsize distribution is preferred. More particularly, independently foreach preference stated: (i) at least, with increasing preference in theorder given, 50, 65, 70, 75, 80, 85, 90, or 95 number percent of theparticles have a size that is at least 62% of the average size; (ii) atleast, with increasing preference in the order given, 40, 50, 60, 65,70, 75, 80, or 85 number percent of the particles have a size that is atleast 76% of the average size; (iii) at least, with increasingpreference in the order given, 20, 30, 40, 45, 50, 55, or 60 numberpercent of the particles have a size that is at least 86% of the averagesize; (iv) not more than, with increasing preference in the order given,40, 30, 25, 20, or 15 number percent of the particles have a size thatis at least 114% of the average size; (v) not more than, with increasingpreference in the order given, 20, 15, 12, 10, 8, 6, or 4 number percentof the particles have a size that is at least 124% of the average size;and (vi) not more than 1 number percent of the particles have a sizethat is at least 170% of the average size.

The outer surface of the dispersed non-film-forming particles is, bydefinition of component (D), an organic substance, preferably anon-film-forming polymer, but the interior of these particles may beand, at least for economy preferably is, a gas, most preferably air.Particles of this type, dispersed in liquid water, are commerciallyavailable from Rohm and Haas Co. under the trademark ROPAQUE™, withdesignating indicia OP-62 LO and OP-96. Gas-filled polymer-walledparticles of this type have the interesting property that they actoptically as opaque, substantially white, pigments. However, it has beenfound that once the particles are incorporated into an autodepositedcoating, if the coating is heated sufficiently, it can be madeirreversibly transparent. Thus by using these materials as component(D), white and other light opaque colors for autodeposited coatings canbe obtained, or transparent autodeposited coatings can be obtained withsufficient heating. Light-colored opaque autodeposited coatings have notheretofore been practically available, although possibilities forobtaining such optical properties for autodeposited coatings have beentaught in various patents.

Irrespective of its exact chemical and/or structural nature, when an atleast initially non-transparent dried and cured autodeposited coating isdesired from a process according to this invention, component (D) ispreferably present in the autodepositing composition used in a volume,measured in milliliters (hereinafter usually abbreviated as “ml”), thathas a ratio to the combined mass, measured in grams (hereinafter usuallyabbreviated as “g”), of the total of components (A) and (E) in the samecomposition that is at least, with increasing preference in the ordergiven, 0.01, 0.03, 0.05, 0.070, 0.080, 0.090, or 0.100 ml/g. The volumeof component (D) to be used in determining this ratio includes not onlythe volume of the solid part of component (D) but also the volume of anygas contained within any gas-tight solid walled space(s) withinparticles of component (D). Furthermore, when the cost per unit volumefrom component (D) that is incorporated into the dried and curedautodeposited coating formed in a process according to the invention islower than the cost per the same unit of volume incorporated fromcomponents (A) and (B) into the dried and cured autodeposited coating,it is still more preferred, at least for economy, for the amount ofcomponent (D) in an autodeposited coating according to the invention tohave a volume to mass ratio of component (D) to combined components (A)and (B) that is at least, with increasing preference in the order given,0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.64 ml/g,inasmuch as it has been found that the corrosion resistance of theautodeposited coating produced does not appear to be adversely affectedby these ratios of component (D) to combined components (A) and (B).

Independently, in order to assure coating integrity, it is preferredthat the ratio of the volume of component (D) to the mass of combinedcomponents (A) and (B) as defined above should not be greater than, withincreasing preference in the order given, 2.0, 1.7, 1.4, 1.2, 1.0, or0.8 ml/g.

Pigment and/or filler component (E) and soluble colorant component (F)may generally be selected for compositions according to this inventionfrom materials established as satisfactory for similar uses in otherorganic film-forming liquid compositions, particularly in priorautodeposition baths. Whether either or both of these optionalcomponents are preferably present in a composition according to theinvention depends primarily on whether an additionally pigmented and/orotherwise colored coating is desired. If it is, suitable pigmentsinclude, for example, carbon black, phthalocyanine blue, phthalocyaninegreen, quinacridone red, benzidene yellow, and titanium dioxide. Anypigments or soluble colorants that tend to react chemically with otherconstituents of a composition according to the invention or todestabilize any dispersed particles present in the composition shouldnormally be avoided. Any pigment and/or soluble colorant used should beadded to the composition in an amount which imparts to the coating thedesired color and/or the desired depth or degree of hue. It should beunderstood that the specific amount used will be governed by thespecific coloring materials used and the color of coating desired.

Generally, the presence of a coalescing agent component (G) in anautodepositing liquid composition according to the invention ispreferred when component (A) is selected as described for the firstespecially preferred embodiment as described above, because without sucha component the autodeposited coatings are usually very susceptible toblister formation, cracking, and/or debonding from the substrate duringdrying. This component is preferably selected from the group consistingof monoethers and monoesters of glycols, preferably glycols with atleast one terminal hydroxy group. Monoethers of ethylene glycol arereadily available and are effective in reducing the density of coatingirregularities, but these monoethers of ethylene glycol are restrictedin use by anti-pollution laws in many locations and also have been foundto be more likely than monoethers of propylene glycol to destabilize theemulsions formed in products according to the invention. Therefore,monoethers of propylene glycol, particularly the n-butyl and phenylmonoethers of propylene glycol, are preferred among the monoethers. Aparticularly preferred monoester is the mono 2-methyl propionate of2,2,4-trimethyl-1,3-pentanediol; this is the most preferred of allmaterials for component (G).

Examples of preferred, commercially available coalescing agents areshown in Table 1.

TABLE 1 Boiling % in Saturated Coalescing Agent Molecular Point, AqueousTrade Name Chemical Name Weight ° C. Solution Dowanol ™ PM Propyleneglycol monomethyl ether 90.1 120.1 Miscible Dowanol ™ PtB Propyleneglycol mono-t-butyl ether 132.2 151* 14.5 Dowanol ™ PnB Propylene glycolmono-n-butyl ether 132.2 170.2 6.4 Dowanol ™ DPnB Dipropylene glycolmono-n-butyl ether 190.3 229 5 Dowanol ™ TPM Tripropylene glycolmonomethyl ether 206.3 242.4 Miscible Dowanol ™ PPh Propylene glycolmonophenyl ether 152.2 242.7 5.4 Texanol ™2,2,4-trimethyl-1,3-pentanediol mono-2-ethyl 216.3 244-247 <0.1propionate Footnote for Table 1 *This material forms an azeotrope withwater that boils at 95° C.

Irrespective of its exact chemical composition, the percentage ofcomponent (G) in an autodepositing liquid composition according to theabove described first especially preferred embodiment of the inventionpreferably is, with increasing preference in the order given, at least5, 10, 12, 14, 16, 18, or 20% of the total solids in component (A) ofthe same autodepositing liquid composition as described above andindependently preferably is, with increasing preference in the ordergiven, not more than 30, 28, 26, 24, or 22% on the same basis.

In contrast, for the second especially preferred embodiment as describedabove, component (G) is not needed and is therefore preferably omittedfor economy. For other types of polymers for component (A), thepreference or lack of preference for coalescing agent (G) may beinferred from experience with prior art autodepositing compositions thatcontain the same type of polymer for component (A).

Optional solvent component (H) may be required during the preparation ofautodepositing liquid compositions according to this invention, but itis not believed in most cases to contribute any desirable characteristicto the final autodepositing liquid compositions formed, and may evenreduce the storage stability of these autodepositing liquidcompositions. Therefore, when not needed, as it is not when either ofthe two especially preferred types of component (A) already describedabove, solvent component (H) is preferably omitted altogether. Whensolvent is required during preparation, as for example forautodepositing compositions in which a substantial amount of epoxy resinis incorporated, the solvent thus required may be later removed, whendesired or necessary to comply with anti-pollution requirements, bymeans known in the art, such as distillation under reduced pressure of amixture of the solvent and the desired active ingredient at atemperature at which the active ingredient will remain liquid, beforeformation of an oil-in-water type dispersion of the desired finalcomponents of an autodepositing liquid composition according to theinvention. However, in some instances the solvents do not unacceptablydiminish the technical benefits of the final autodepositing liquidcompositions according to the invention, and may be left in place in theautodepositing liquid compositions according to the invention if legalrequirements are not thereby violated. Any such residual solvent willnormally be expelled during cure of the autodeposited coatings.

Any material effective as a plasticizer, for example those known in theart such as di(2-ethylhexyl) phthalate, may be used as optionalcomponent (J). Ordinarily, however, if one of the two especiallypreferred types of polymer component (A) is used, no such externalplasticizer will be needed.

There are no particular difficulties involved in preparing anautodeposition composition according to the invention; the componentsmay simply be mixed together, once both components (A) and (D) have beenadequately emulsified separately, with anionic emulsifiers, to remainsuspended in aqueous solutions. Normally, component (C) is added only ashort time before beginning to use an autodeposition composition.

A process according to the invention for using an autodepositing liquidcomposition according to the invention in its simplest form comprises,preferably consists essentially of, or more preferably consists of,operations of:

(I) contacting a solid surface, which is capable of reacting with anautodeposition bath according to the invention to generate cations witha valence of at least two dissolved in the autodeposition bath, with anautodeposition bath according to the invention as described above for asufficient time to form over the contacted solid surface a wetcontinuous coating which contains molecules derived from component (A)and particles derived from component (D) of the autodepositing liquidcomposition according to the invention, the wet continuous coating beingsufficiently coherent and adherent to the solid surface for at leastsome part thereof to remain on the solid surface against the force ofnatural ambient gravity when the solid surface and any non-adherent partof the autodepositing liquid composition according to the invention areremoved from contact with each other;

(II) after operation (I) as described immediately above, removing thewet continuous coating formed over the solid surface from contact withany non-adherent part of the autodepositing liquid composition accordingto the invention with which it was contacted in operation (I) and,optionally, rinsing the coating with at least one liquid rinsecomposition that is not an autodepositing liquid composition; and

(III) after operation (II), expelling from the wet continuous coating asufficient amount of water and, optionally, other materials so as toconvert it into a dry continuous solid coating in place over the solidsurface contacted in operation (I).

All operations of a conventional autodeposition process after theformation of the wet autodeposited coating containing characterizingcomponent (D) according to this invention may be performed in the samemanner for a process according to this invention as for a prior artprocess, except that the susceptibility of the opacity developed in anautodeposited coating according to the above noted preferred embodimentsof this invention to be converted to transparency by heating must not belost sight of. As a result of this susceptibility, when anon-transparent coating is desired, it may be necessary to deviate fromprevious process operations that utilized cure at high temperatures andsubstitute longer cure at lower temperatures. With the most preferredtype of component (D) as indicated above, for example, heating for 15minutes at 176° C. made completely transparent an initially nearlyopaque coating that contained 0.10 ml of component (D) per gram of(dried) component (A) and had been initially cured at 125° C. for 20minutes.

As with prior art autodeposition processes, for most substrate surfacesthe corrosion resistance achieved can be substantially improved byincluding contact between the wet autodeposited coating and a rinseliquid as part of operation (II) as described above. Suitable, but notexhaustively suitable, rinse liquids are described in the following U.S.Patents, each of which, to the extent that it teaches rinsing of wetautodeposited coatings before drying them and is not contrary to anyexplicit statement herein, is hereby incorporated herein by reference:5,667,845 of Sep. 16, 1997 to Roberto et al.; 5,342,694 of Aug. 30, 1994to Ahmed et al.; 5,248,525 of Sep. 28, 1993 to Siebert; and 4,637,839 ofJan. 20, 1987 to Hall. More particularly, for the first especiallypreferred embodiment of the invention as described above, which utilizesacrylic film-forming resin, rinse liquids that contain hexavalentchromium, optionally along with some trivalent chromium, are preferred,while for the second especially preferred embodiment as described above,which utilizes polymers of predominantly vinylidene chloride as thefilm-forming resin component, rinse liquids with ammonium bicarbonateare preferred.

The rinse solution may be contacted, in a process according to theinvention, with a wet uncured autodeposited coating by any convenientmethod or combination of methods, such as spraying, curtain coating, orimmersion, with the latter normally preferred. Preferably the time ofcontact between the rinse solution and the wet uncured autodepositedcoating is, with increasing preference in the order given, not less than5, 10, 20, 30, 40, 45, 50, 55, or 60 seconds (hereinafter oftenabbreviated as “sec”) and independently preferably is, with increasingpreference in the order given, not more than 600, 400, 200, 120, 110,100, 95, or 90 sec. The temperature of the rinse solution during contactwith a wet uncured autodeposited coating may be any temperature at whichthe rinse solution is liquid but normally preferably is, with increasingpreference in the order given, not less than 10, 15, 18, or 20° C. andindependently preferably, primarily for reasons of economy, is not morethan, with increasing preference in the order given, 60, 45, 35, 30, 27,25, or 23° C.

After the reaction rinse treatment, the wet autodeposited coating asmodified by contact with the reaction rinse is sometimes rinsed againwith water, preferably deionized water if any, before being dried and,if desired as is usually preferred, cured by heating at an elevatedtemperature so selected that the protective properties of the coatingare fully developed but not adversely affected. The temperature and timeof treatment will depend on the nature of the particular film-formingresin, i.e., component (A), in the autodeposited coating and thethickness of the coating. With autodeposition baths containing mosttypes of acrylic organic film-forming resins, the autodeposited coatingspreferbly are heated, during or after drying, to a temperature that is,with increasing preference in the order given, at least 90, 100, 110,120, 130, 140, or 145° C. and independently preferably is, withincreasing preference in the order given, not more than 230, 220, 200,190, 180, 170, 160, or 165° C. When the film-forming resin used consistspredominantly of vinylidene chloride residues, maximum temperature towhich the resulting autodeposited coating is heated during its dryingand curing preferably is at least, with increasing preference in theorder given, 30, 50, 70, 80, 85, 90, 95, or 100° C. and independentlypreferably is not more than, with increasing preference in the ordergiven, 150, 140, 130, 125, 120, 115, 110, or 105° C.

Times of heating for curing preferably range from 5 seconds up to 30minutes, dependent on the mass of the coated article. Preferably, thecoating is heated for a period of time until the metallic substrate hasreached the temperature of the heated environment, typically in a forcedair baking oven.

The invention and its benefits may be further appreciated from theworking examples and comparison examples set forth below.

PREPARATION AND USE OF COMPOSITIONS INCLUDING DISPERSED NON-FILM-FORMINGORGANIC PARTICLES Group 1 With Acrylic Polymer Film-Forming Resin

In these examples, RHOPLEX™ WL-91 acrylic latex (hereinafter usuallyabbreviated as “WL-91”) commercially supplied by Rohm & Haas Co.,usually diluted with additional water, and with DOWFAX™ 2A1 surfactant(hereinafter usually abbreviated as “2A1”) added as supplementalemulsifying agent, was used as a primary precursor dispersion supplyingall of film-forming polymer component (A) and at least part ofemulsifying agent component (B) of an eventual autodepositing liquidcomposition according to the invention. This WL-91 product is reportedby its supplier to contain 41-42% of solids, of which at least 95% isbelieved to be acrylic polymer solids and any remainder to beemulsifying agent; the chemical nature and exact amount of theemulsifying agent are not disclosed by the supplier. ROPAQUE™ OP-96pigment dispersion (hereinafter usually abbreviated as “OP-96”)commercially supplied by Rohm and Haas Co. was the source of component(D); according to its supplier, this material contains 30.5% solids inthe form of particles averaging 0.55 μm in size and normally having atleast one airfilled interior space per particle, so that the volumepercent of the total dispersion occupied by its solid content and thegas-tight spaces within the particles of its solids content is 50%, andeach gram of the dried dispersion occupies 1.59 ml of volume.

A base autodeposition bath was prepared; it consisted of, in addition towater: 5.7% of solids from WL-91; 1.21% of Texanol™ coalescing agent;0.04% of 2A1 emulsifying agent; sufficient dissolved hydrofluoric acidto give the total composition a pH of 2.3; sufficient ferric fluoride tosupply, together with the hydrofluoric acid, 1.8 g of fluoride ions perliter of total composition, and sufficient hydrogen peroxide to provide,together with the other components, an oxidizing potential for the totalsolution that was 330 mV more oxidizing than a standard hydrogenelectrode. Successive additions of the OP-96 product were added to thisbase autodeposition bath to produce autodeposition compositionsaccording to the invention with the component (D) volume to component(A) solids ratios shown in Table 2. Standard test panels were given anautodeposited coating by immersion for 90 seconds in most of theseautodeposition compositions according to the invention, which weremaintained at normal ambient temperature of 22±5° C., with otherprocessing conditions also given in Table 2.

TABLE 2 Ratio, Identifying [ml of (D)]/ Drying/Curing Temperature(s) andTime(s) Coating Number(s) [g of (A)] Post Rinse 1st ° C. 1st Min. 2nd °C. 2nd Min. Appearance 1 0.10 Water 125 20 none none Off-white 2 0.10Water 125 20 176 15 Transparent 3 0.10 1087 RR 125 60 none noneOff-white 4 0.10 1087 RR 125 30 145 30 Off-white 5 0.21 1087 RR 125 20none none Off-white 6 0.21 1087 RR 145 20 none none Off-white 7 0.21Water 125 20 none none Whiter than 8 0.21 Water 145 20 none none #'s 1and 2 9, 10 0.21 Water 176 20 none none Transparent 11, 12 0.31 Water145 30 none none Opaque, whiter than #'s 7 and 8 13 0.31 1087 RR 145 25none none Whiter than 14 0.31 1087 RR 145 45 none none #'s 5 and 6 15,16 0.43 Water 145 20 none none Opaque white 17 0.43 1087 RR 145 20 nonenone Whiter than 18 0.43 1087 RR 145 40 none none #'s 13 and 14 19, 200.65 Water 145 20 none none Opaque white 21 0.65 1087 RR 145 20 nonenone Both had 22 0.65 1087 RR 145 40 none none same appearance 23, 240.65 Water 175 20 none none Transparent 25, 26 0.65 1087 RR 175 20 nonenone Brown Abbreviations for Table 2 “Min.” means “minute(s)”; “1087 RR”means “a solution of AUTOPHORETIC ® 1087 Reaction Rinse, commerciallyavailable from Henkel Surface Technologies, Madison Heights, Michigan,used as directed by supplier”; “#” means “number”. Footnote for Table 2*Some chromium is believed to be retained in and to darken the dried andcured coating when 1087 RR is used.

Group 2 With Poly(Vinylidene Chloride) Film-Forming Resin

In these examples, a self-emulsified poly(vinylidene chloride) latexdiluted with additional water was used to supply all of film-formingpolymer component (A) and all of emulsifying agent component (B), exceptfor whatever emulsifying agent is included in OP-96 as described above.As for Group 1, a base autodeposition bath was prepared. For this groupthe base autodeposition bath consisted of, in addition to water: 5.4% ofself-emulsifying film-forming polymer; sufficient dissolved hydrofluoricacid to give the total composition a pH of 2.3; sufficient ferricfluoride to supply, together with the hydrofluoric acid, 1.8 g offluoride ions per liter of total composition, and sufficient hydrogenperoxide to provide, together with the other components, an oxidizingpotential for the total solution that was 330 mV more oxidizing than astandard hydrogen electrode. Successive additions of the OP-96 productwere added to this base autodeposition bath to produce autodepositioncompositions according to the invention with the component (D) volume tocomponent (A) solids ratios shown in Table 3. Standard test panels weregiven an autodeposited coating by immersion for 90 seconds in most ofthese autodeposition compositions according to the invention, which weremaintained at normal ambient temperature of 22±5° C. All of thesecoatings were dried and cured for 20 minutes at 104° C. Other processingconditions are given in Table 3.

TABLE 3 Identifying Ratio, [ml of (D)]/[g Post Rinse Coating Number(s)of (A) and (B)] Liquid Apperarance 27-32 0.12 2150 RR Light yellow*,nearly opaque 33, 34 0.12 Water White, nearly opaque 35, 36 0.37 WaterWhite, opaque 37-40 0.37 2150 RR Yellowed*, opaque Abbreviations forTable 3 “2150 RR” means “a solution of AUTOPHORETIC ®2 150 ReactionRinse, commercially available from Henkel Surface Technologies, MadisonHeights, Michigan, used as directed by supplier”. Footnote for Table 3*More iron is believed to be retained in and to darken the dried andcured coating when 2150 RR is used.

CORROSION TESTING

Some of the test panels prepared in Groups 1 and 2 were conventionallyscribed and subjected to neutral salt spray tests according to AmericanSociety for Testing and Materials Standard Procedure B-117 for 500hours. The ratio of volume of component (D) to mass of component (A)within the range tested had no substantial effect on the corrosionresistance. Higher times and/or temperatures of drying and curingimproved corrosion resistance in Group 1, as expected for similarautodeposited coatings without the addition of component (D) with thistype of film-forming resin. Detailed results are shown in Table 4.

TABLE 4 Creep Width and Any Other Identifying Number(s) Observationsafter 500 Hours 4  4 millimeters 5 16 millimeters 6 14 millimeters 13 16millimeters 14 18 millimeters 17 13 millimeters 18 15 miltimeters 21 15millimeters 22 11 millimeters 25   7 millimeters; creep uneven 27  2millimeters 31  2 millimeters 32  2 millimeters 35 2-3 millimeters  372-3 millimeters ; a few spots of field rust

What is claimed is:
 1. An autodepositing liquid composition comprisingwater and the following components: (A) at least 1.0%, based on thewhole composition, of a component of dissolved, dispersed, or bothdissolved and dispersed film forming polymer molecules; (B) anemulsifying agent component in sufficient quantity to emulsify any waterinsoluble part of any other component so that, in the autodepositingliquid composition, no separation or segregation of bulk phases that isperceptible with normal unaided human vision occurs during storage at25° C. for at least 24 hours after preparation of the autodepositingliquid composition, in the absence of contact of the autodepositingliquid composition with any metal that reacts with the autodepositingliquid composition to produce therein dissolved metal cations with acharge of at least two; (C) a dissolved accelerator component selectedfrom the group consisting of acids, oxidizing agents, and complexingagents that are not part of immediately previously recited components(A) or (B), this accelerator component being sufficient in strength andamount to impart to the total autodepositing liquid composition anoxidation-reduction potential that is at least 100 mV more oxidizingthan a standard hydrogen electrode; and (D) a component of dispersedgas-filled non-film-forming polymer walled particles that are not partof any of immediately previously recited components (A) through (C),wherein the volume, measured in ml, of component (D) in the compositionhas a ratio to the mass, measured in grams, of the total of components(A) and (B) in the same composition that is at least about 0.01 ml/g. 2.An autodepositing liquid composition comprising water and the followingcomponents (A) at least 1.0%, based on the whole composition, of acomponent of dissolved, dispersed, or both dissolved and dispersed filmforming polymer molecules selected from molecules that contain thefollowing subcomponents in the amounts indicated below: (A1) from about2.0 to about 7.0 percent of a subcomponent selected from residues ofpolymerization of acrylic and methacrylic acids and the salts of both ofthese acids; (A2) from about 15 to about 50 percent of a subcomponentselected from residues of polymerization of esters of acrylic andmethacrylic acids with alcohols that contain at least 4 but not morethan 20 carbon atoms per molecule; (A3) from about 10 to about 50percent of a subcomponent selected from residues ofaddition-polymerizable hydrocarbon molecules; and (A4) from about 10 toabout 40 percent of a subcomponent of residues of acrylic monomers thatare not part of either subcomponent (A1) or (A2) as describedimmediately above; (B) an emulsifying agent component in sufficientquantity to emulsify any water insoluble part of any other component sothat, in the autodepositing liquid composition, no separation orsegregation of bulk phases that is perceptible with normal unaided humanvision occurs during storage at 25° C. for at least 24 hours afterpreparation of the autodepositing liquid composition, in the absence ofcontact of the autodepositing liquid composition with any metal thatreacts with the autodepositing liquid composition to produce thereindissolved metal cations with a charge of at least two; (C) a dissolvedaccelerator component selected from the group consisting of acids,oxidizing agents, and complexing agents that are not part of immediatelypreviously recited components (A) or (B), this accelerator componentbeing sufficient in strength and amount to impart to the totalautodepositing liquid composition an oxidation-reduction potential thatis at least 100 mV more oxidizing than a standard hydrogen electrode,wherein component (C) is comprised of the following three subcomponents:(C1) from about 0.8 to about 4.0 g/l of fluoride ions; (C2) an amount ofoxidizing agent that provides to the autodepositing liquid compositionan oxidation potential that is from about 200 to about 500 mV moreoxidizing than a standard hydrogen electrode; and (C3) a source ofhydrogen cations in an amount sufficient to impart to the autodepositionbath a pH that is from about 1.0 to about 3.8; and (D) a component ofdispersed non-film-forming organic particles that are not part of any ofimmediately previously recited components (A) through (C).
 3. Anautodepositing liquid composition according to claim 2, wherein:component (A) is selected from molecules that contain the followingsubcomponents in the amounts indicated below: (A1) from about 3.5 toabout 6.5 percent of a subcomponent selected from residues ofpolymerization of methacrylic acid and its salts; (A2) from about 26 toabout 39 percent of a subcomponent selected from residues ofpolymerization of esters of acrylic and methacrylic acids with alcoholsthat contain at least 8 but not more than 10 carbon atoms per molecule;(A3) from about 32 to about 44 percent of a subcomponent selected fromresidues of addition-polymerizable hydrocarbon molecules that contain anaromatic nucleus; and (A4) from about 17 to about 30 percent of asubcomponent of residues of acrylic monomers that are not part of eithersubcomponent (A1) or (A2) as described immediately above; component (C)contains the following three subcomponents: (C1) from about 1.60 toabout 2.10 g/l of fluoride ions; (C2) an amount of hydrogen peroxide andferric ions that provides to the autodepositing liquid composition anoxidation potential that is from about 350 to about 400 mV moreoxidizing than a standard hydrogen electrode; and (C3) a source ofhydrogen cations in an amount sufficient to impart to the autodepositionbath a pH that is from about 2.0 to about 2.6; and there is alsocontained a component (G) selected from the group consisting ofmonoethers and monoesters of glycols with at least one terminal hydroxygroup, the mass of component (G) being from about 10 to about 30% of themass of solids in component (A) of the same composition.
 4. Anautodepositing liquid composition according to claim 1, wherein:component (A) incorporates component (B) and is selected from moleculesincluding residues of vinylidene chloride that constitute from 50 to 99%of the mass of the molecules and residues of sulfoethylmethacrylate thatconstitute from 0.1 to 5% of the mass of the molecules and, optionally,residues of one or more other comonomers selected from the groupconsisting of vinyl chloride, acrylonitrile, acrylamides, andmethacrylamides; and component (C) contains the following threesubcomponents: (C1) from about 0.8 to about 4.0 g/l of fluoride ions;(C2) an amount of oxidizing agent that provides to the autodepositingliquid composition an oxidation potential that is from about 200 toabout 500 mV more oxidizing than a standard hydrogen electrode; and (C3)a source of hydrogen cations in an amount sufficient to impart to theautodeposition bath a pH that is from about 1.0 to about 3.8.
 5. Anautodepositing liquid composition according to claim 4, whereincomponent (C) contains the following three subcomponents: (C1) fromabout 1.60 to about 2.10 g/l of fluoride ions; (C2) an amount ofhydrogen peroxide and ferric ions that provides to the autodepositingliquid composition an oxidation potential that is from about 350 toabout 400 mV more oxidizing than a standard hydrogen electrode; and (C3)a source of hydrogen cations in an amount sufficient to impart to theautodeposition bath a pH that is from about 2.0 to about 2.6.
 6. Anautodepositing liquid composition according to claim 1, wherein:component (D) is selected from said gas-filled non-film-forming polymerwalled particles having sizes such that: the average size of theparticles, based on their largest linear dimension, is from about 0.2 toabout 1.0 μm; at least about 75 number percent of the particles have asize that is at least 62% of the average size; at least about 70 numberpercent of the particles have a size that is at least 76% of the averagesize; at least about 50 number percent of the particles have a size thatis at least 86% of the average size; not more than about 25 numberpercent of the particles have a size that is at least 114% of theaverage size; not more than about 10 number percent of the particleshave a size that is at least 124% of the average size; and not more thanabout 1 number percent of the particles have a size that is at least170% of the average size; the volume, measured in ml, of component (D)in the composition has a ratio to the mass, measured in grams, of thetotal of components (A) and (B) in the same composition that is within arange from 0.20 to 2.0 ml/g.
 7. An autodepositing liquid compositionaccording to claim 4, wherein: component (D) is selected from saidgas-filled non-film-forming polymer walled particles having sizes suchthat: the average size of the particles, based on their largest lineardimension, is from about 0.2 to about 1.0 μm; at least about 75 numberpercent of the particles have a size that is at least 62% of the averagesize; at least about 70 number percent of the particles have a size thatis at least 76% of the average size, at least about 50 number percent ofthe particles have a size that is at least 86% of the average size; notmore than about 25 number percent of the particles have a size that isat least 114% of the average size; not more than about 10 number percentof the particles have a size that is at least 124% of the average size;and not more than about 1 number percent of the particles have a sizethat is at least 170% of the average size; and the volume, measured inml, of component (D) in the composition has a ratio to the mass,measured in grams, of the total of components (A) and (B) in the samecomposition that is within a range from 0.20 to 2.0 ml/g.
 8. Anautodepositing liquid composition according to claim 3, wherein:component (D) is selected from said gas-filled non-film-forming polymerwalled particles having sizes such that: the average size of theparticles, based on their largest linear dimension, is from about 0.2 toabout 1.0 μm; at least about 75 number percent of the particles have asize that is at least 62% of the average size; at least about 70 numberpercent of the particles have a size that is at least 76% of the averagesize; at least about 50 number percent of the particles have a size thatis at least 86% of the average size; not more than about 25 numberpercent of the particles have a size that is at least 114% of theaverage size; not more than about 10 number percent of the particleshave a size that is at least 124% of the average size; and not more thanabout 1 number percent of the particles have a size that is at least170% of the average size; and the volume, measured in ml, of component(D) in the composition has a ratio to the mass, measured in grams, ofthe total of components (A) and (B) in the same composition that iswithin a range from 0.20 to 2.0 ml/g.
 9. An autodepositing liquidcomposition according to claim 2, wherein: component (D) is selectedfrom said gas-filled non-film-forming polymer walled particles havingsizes such that: the average size of the particles, based on theirlargest linear dimension, is from about 0.2 to about 1.0 μm; at leastabout 75 number percent of the particles have a size that is at least62% of the average size; at least about 70 number percent of theparticles have a size that is at least 76% of the average size; at leastabout 50 number percent of the particles have a size that is at least86% of the average size; not more than about 25 number percent of theparticles have a size that is at least 114% of the average size; notmore than about 10 number percent of the particles have a size that isat least 124% of the average size; and not more than about 1 numberpercent of the particles have a size that is at least 170% of theaverage size; and the volume, measured in ml, of component (D) in thecomposition has a ratio to the mass, measured in grams, of the total ofcomponents (A) and (B) in the same composition that is within a rangefrom 0.20 to 2.0 ml/g.
 10. An autodepositing liquid compositionaccording to claim 1, wherein: the volume, measured in ml, of component(D) in the composition has a ratio to the mass, measured in grams, ofthe total of components (A) and (B) in the same composition that is atleast about 0.09 ml/g.
 11. A process for forming an autodepositedcoating, said process comprising operations of: (I) contacting a solidsurface, which is capable of reacting with an autodepositing liquidcomposition to generate cations with a valence of at least two dissolvedin an autodepositing liquid composition, with an autodepositing liquidcomposition according to claim 1 for a sufficient time to form over thecontacted solid surface a wet continuous coating which containsmolecules derived from component (A) and particles derived fromcomponent (D) of the autodepositing liquid composition, the wetcontinuous coating being sufficiently coherent and adherent to the solidsurface for at least some part thereof to remain on the solid surfaceagainst the force of natural ambient gravity when the solid surface andany non-adherent part of the autodepositing liquid composition accordingto the invention are removed from contact with each other; (II) afteroperation (I) as described immediately above, removing the wetcontinuous coating formed over the solid surface from contact with anynon-adherent part of the autodepositing liquid composition according tothe invention with which it was contacted in operation (I) and,optionally, rinsing the coating with at least one liquid rinsecomposition that is not an autodepositing liquid composition; and (III)after operation (II), expelling from the wet continuous coating asufficient amount of water and, optionally, other materials so as toconvert it into a dry continuous solid coating in place over the solidsurface contacted in operation (I).
 12. A process according to claim 11,wherein: the autodepositing liquid composition utilized in operation (I)comprises a component (D) that is selected from said gas-fillednon-film-forming polymer walled particles that act as a white pigmentfor the autodepositing liquid composition; the volume, measured in ml,of said gas-filled non-film-forming-polymer-walled particles in thecomposition has a ratio to the mass, measured in grams, of the total ofcomponents (A) and (B) in the same composition that is at least about0.10 ml/g; and in operation (III), the temperature of the solid coatingis controlled so that the autodeposited coating does not becometransparent.
 13. A liquid replenisher composition that comprises waterand: (A′) at least 10%, based on the whole composition, of dissolved,dispersed, or both dissolved and dispersed film forming polymermolecules; (B′) an emulsifying agent component in sufficient quantity toemulsify any water insoluble part of any other component so that, in theliquid replenisher composition, no separation or segregation of bulkphases that is perceptible with normal unaided human vision occursduring storage at 25° C. for at least 24 hours after preparation of theliquid replenisher composition, in the absence of contact of the liquidreplenisher composition with any metal that reacts with the liquidreplenisher composition to produce therein dissolved metal cations witha charge of at least two; and (D′) a component of dispersed gas-fillednon-film-forming polymer walled particles that are not part of either ofimmediately previously recited components (A′) or (B′), wherein thevolume, measured in ml, of component (D) in the composition has a ratioto the mass, measured in grams, of the total of components (A) and (B)in the same composition that is at least about 0.01 ml/g.
 14. A liquidreplenisher composition comprising water and: (A′) at least 10%, basedon the whole composition, of dissolved, dispersed, or both dissolved anddispersed film forming polymer molecules selected from molecules thatcontain the following subcomponents in the amounts indicated below:(A′1) from about 2.0 to about 7.0 percent of a subcomponent selectedfrom residues of polymerization of acrylic and methacrylic acids and thesalts of both of these acids; (A′2) from about 15 to about 50 percent ofa subcomponent selected from residues of polymerization of esters ofacrylic and methacrylic acids with alcohols that contain at least 4 butnot more than 20 carbon atoms per molecule; (A′3) from about 10 to about50 percent of a subcomponent selected from residues ofaddition-polymerizable hydrocarbon molecules; and (A′4) from about 10 toabout 40 percent of a subcomponent of residues of acrylic monomers thatare not part of either subcomponent (A′1) or (A′2) as describedimmediately above; (B′) an emulsifying agent component in sufficientquantity to emulsify any water insoluble part of any other component sothat, in the liquid replenisher composition, no separation orsegregation of bulk phases that is perceptible with normal unaided humanvision occurs during storage at 25° C. for at least 24 hours afterpreparation of the liquid replenisher composition, in the absence ofcontact of the liquid replenisher composition with any metal that reactswith the liquid replenisher composition to produce therein dissolvedmetal cations with a charge of at least two; and (D′) a component ofdispersed non-film-forming organic particles that are not part of eitherof immediately previously recited components (A′) or (B′).
 15. A liquidreplenisher composition according to claim 14, wherein: component (A′)is selected from molecules that contain the following subcomponents inthe amounts indicated below: (A′1) from about 3.5 to about 6.5 percentof a subcomponent selected from residues of polymerization ofmethacrylic acid and its salts; (A′2) from about 26 to about 39 percentof a subcomponent selected from residues of polymerization of esters ofacrylic and methacrylic acids with alcohols that contain at least 8 butnot more than 10 carbon atoms per molecule; (A′3) from about 32 to about44 percent of a subcomponent selected from residues ofaddition-polymerizable hydrocarbon molecules that contain an aromaticnucleus; and (A′4) from about 17 to about 30 percent of a subcomponent(A′4) of residues of acrylic monomers that are not part of eithersubcomponent (A′1) or (A′2) as described immediately above; and there isalso contained a component (G′) selected from the group consisting ofmonoethers and monoesters of glycols with at least one terminal hydroxygroup, the mass of component (G′) being from about 10 to about 30% ofthe mass of solids in component (A′) of the same composition.
 16. Aliquid replenisher composition according to claim 13, wherein component(A′) incorporates component (B′) and is selected from moleculesincluding: residues of vinylidene chloride that constitute from 50 to99% of the mass of the molecules; and residues of sulfoethylmethacrylatethat constitute from 0.1 to 5% of the mass of the molecules; and,optionally, residues of one or more other comonomers selected from thegroup consisting of vinyl chloride, acrylonitrile, acrylamides, andmethacrylamides.
 17. A liquid replenisher composition according to claim13, wherein: component (D′) is selected from said gas-fillednon-film-forming polymer walled particles having sizes such that: theaverage size of the particles, based on their largest linear dimension,is from about 0.2 to about 1.0 μm; at least about 75 number percent ofthe particles have a size that is at least 62% of the average size; atleast about 70 number percent of the particles have a size that is atleast 76% of the average size; at least about 50 number percent of theparticles have a size that is at least 86% of the average size; not morethan about 25 number percent of the particles have a size that is atleast 114% of the average size; not more than about 10 number percent ofthe particles have a size that is at least 124% of the average size; andnot more than about 1 number percent of the particles have a size thatis at least 170% of the average size; and the volume, measured in ml, ofcomponent (D′) in the composition has a ratio to the mass, measured ingrams, of the total of components (A′) and (B′) in the same compositionthat is within a range from 0.20 to 2.0 ml/g.
 18. A liquid replenishercomposition according to claim 14, wherein: component (D′) is selectedfrom said gas-filled non-film-forming polymer walled particles havingsizes such that: the average size of the particles, based on theirlargest linear dimension, is from about 0.2 to about 1.0 μm; at leastabout 75 number percent of the particles have a size that is at least62% of the average size; at least about 70 number percent of theparticles have a size that is at least 76% of the average size; at leastabout 50 number percent of the particles have a size that is at least86% of the average size; not more than about 25 number percent of theparticles have a size that is at least 114% of the average size; notmore than about 10 number percent of the particles have a size that isat least 124% of the average size; and not more than about 1 numberpercent of the particles have a size that is at least 170% of theaverage size; and the volume, measured in ml, of component (D′) in thecomposition has a ratio to the mass, measured in grams, of the total ofcomponents (A′) and (B′) in the same composition that is within a rangefrom 0.20 to 2.0 ml/g.
 19. An autodepositing liquid compositionaccording to claim 1 wherein the gas in the gas-filled non-film-formingpolymer walled particles of component (D) is air.
 20. An liquidreplenisher composition according to claim 13 wherein the gas in thegas-filled non-film-forming polymer walled particles of component (D) isair.